Whilst not tram related this article takes a fascinating look at the inventor and development of air filled rubber tyres.
This article looks at one of the somewhat forgotten Scottish Inventors of the 19th Century.
Scotland has always been associated with famous inventions. We all know of the famous Scottish Inventors – Thomas Telfer (road and bridges); John Loudon Macadam (tarmac); John Logie Baird (television); Alexander Graham Bell (the telephone); James Watt (fixed steam engines and steam engine pioneer); Charles Macintosh (water-proofing); James Naysmith (Steam hammer used in forging); but who was Robert William Thomson ?
Robert Thomson was born in Stonehaven, Aberdeenshire, in 1822, and died due to ill health at the age of 50 at his home at 3 Moray Place Edinburgh. He tried various vocations before commencing his own business in 1844.
Thomson’s Patents and Developments:
· The pneumatic tyre
· Improvements in obtaining and applying motive power
· Steam boilers and the improvements in steam gauges
· Steam omnibuses
· Applying steam power in agriculture
· The self-filling pen
· Light weight road steamers
· Guiding road streamers on street tramways
· Elastic tyres, beds, seats and other supports or cushions.
· Using explosives to break up hard substances such as rock stone and coal
This article concentrates on two Patents which were of importance to the development of Transport in Scotland.
The pneumatic rubber tyre, or "aerial wheel" as Thomson called it, would eventually transform road travel by providing a cushion of air between the road surface and the actual vehicle.
Thomson was only 23 years old when he patented his pneumatic tyre. His tyre invention consisted of a hollow belt of India rubber inflated with air so that the wheels presented "a cushion of air to the ground, rail or track on which they run". This elastic belt of rubberised canvas was enclosed within a strong outer casing of leather which was bolted to the wheel. Thomson's "Aerial Wheels" were demonstrated in Regent Park London in March 1847 and were fitted to several horse-drawn carriages, greatly improving the comfort of travel and reducing noise.
This patent also included the idea of the first rubber tyred metro. A railway was illustrated, with the weight carried by pneumatic main wheels running on a flat board track and guidance provided by small horizontal steel wheels running on the sides of a central vertical guide rail. An early version of the later guided bus way or the system similar to that used on the Paris Metro.
For many years Thomson was frustrated by the lack of thin rubber, and he turned to the development of his solid rubber tyres. It was later, in 1867 that he patented a solid India rubber tyre for his road steamers which he was developing and one of the inventions he is most associated with.
It was not until 43 years later that the pneumatic tyre returned, when it was developed as a bicycle tyre by John Boyd Dunlop. Dunlop was granted a patent in 1888, but two years later was officially informed that it was invalid as Thomson's patent predated it.John Boyd Dunlop who lived between 5th February 1840 and 23rd October 1921 was born in Dreghorn, North Ayrshire. He founded the rubber company that bears his name, the Dunlop Rubber Co. and the Dunlop Pneumatic Tyre Co., which is now associated with Dunlop tyres. He is often mistaken for the inventor of the pneumatic tyre, which he patented on 7th December 1888. He can claim to have invented the bicycle wheel inner tube. As noted his patent was later rescinded because the invention of a pneumatic tyre had already been patented by Robert Thomson in 1846. Dunlop’s name continues and is familiar today on rubber based tyres.
The application of vulcanised (Vulcanisation is the process of changing the physical properties of rubber through application of sulphur and heat) India-rubber to the wheels of road steamers was described at the time as one of “the greatest step which had ever been made in the use of steam on common roads".
In 1922 the Royal Scottish Automobile Club presented the town of Stonehaven with a bronze plaque to mark the centenary of Robert William Thomson's birth and in recognition of his invention of the pneumatic tyre. This plaque was placed on the building on the south side of Market Square which occupies the site of his birthplace.
The application of steam to urban transport involved some difficulties in placating public opinion. Locomotive developers required to make the engines silent, make sure that no smoke or steam was emitted, and that no exposed parts were visible, all to ensure that no danger or alarm was caused to horses or pedestrians. This was at the time where a boy was required to walk in front of any moving mechanical vehicle waving a red flag.
The resilience of the stout vulcanised rubber tyres allowed Thomson’s lightweight five ton steam engine to run on “hard or soft, wet or dry surfaces, over obstacles, uphill or downhill”. In addition, the thick rubber tyres did not damage the roads as did the iron wheels of heavy traction engines. Thomson's first road steamers, manufactured in his own small workshop in Leith, were fitted with three wheels, the small single wheel at the front being directly below the steering wheel. The tyres, which were 125 mm (5") thick, were corrugated internally and adhered to the wheel by friction.
The 1870 Report
In the 1870s anxiety was being expressed on the account of the work required by horses. A Parliamentary Paper was issued in August of 1870 suggesting the earlier invention by Thomson of a light weight road steamer was far more useful than any horse could ever be “except for hunting”.
Mr. Thomson design was a 6hp traction engine with a vertical boiler and weighing about 5 tons which he had built by T. M. Tennant and Co. of the Bowershall Works in Edinburgh. This was fitted with vulcanised rubber tyres to the wheels and the Scotsman Newspaper announced that the engine was "in advance of everything which had preceded it." The steam cylinder was 5 in. diameter, and 8 in. stroke. The engine was mounted upon three wheels, all of which were fitted with rubber tyres, the driving wheel tyres being 12 in. wide and 5 in. thick.
The Report came to the conclusion “that the question of steam traction on common roads is now completely solved”…; “…that the application of the india rubber tire is a perfect success, that it opens up an entirely new field, and that the application was more a discovery than an invention.” The wheel and tyre were described as having narrow flanges, upon which was placed a ring of soft vulcanized india rubber, “…that it about 12 inches in width and five inches in thickness, which thus surrounds the iron tire and is kept in its place by flanges, then over the india rubber there is placed an endless chain of steel plates which is the portion of the wheel that comes into contact with the rough road, the reticulated chain being connected by a sort of vertebra at each side of the wheel. The India rubber tire and this ring of steel plates have no rigid connection, but are at perfect liberty to move around as they please without consulting each other or even without the concurrence of the inner ring of the wheel which they both enclose. The reason for the efficiency is because the soft India rubber allows it to flatten upon the road whether rough or smooth. The wheel being a circle fit is a rigid structure, presents but a small surface, but this wheel conforms to every irregularity for a space of nearly two feet by the weight of the engine causing thee India rubber to collapse and so producing a change of form…” The tyre of rubber, the holding plate, all sat on a flanged steel wheel. The weight of the road steamer causing the rubber to flatten when it ran over the road, providing a smooth ride as it eliminated the changes in the road surface. The steel or wooden wheels which were generally in use at that time fell into all the holes and ruts left in the surface making the journey uncomfortable and slow.
The road steamer as invented by Thomson and using the solid tyres had a greater proportion of the weight, including the boiler, resting upon the rear two driving wheels, with the front single wheel used for guiding the direction of travel. The boiler had a copper pot for holding the water within the furnace and it was built so that if the boiler contained any water the pot would always have a full supply. This gave the road steamer a low centre of gravity and made it far more maneuverable, allowing the engine to run up a 1 in 10 hill, or travel at an angle up to 35 degrees.
Early trials took place in Leith. On the first trial the contemporary reports state that the streets were very wet. “…A train of wagons containing 10 tons of flour besides their own weight were standing at the bottom of a slippery street with a gradient of about 1 in 17. To this train the little engine was attached and away it marched as if it had no load at all, went to the top of the hill and then down the other side with no brakes being required…”; “…after depositing the load in Leith it ran down to Portobello seashore at the rate off about 10 m p h. On surveying the sand it was thought impossible that it could travel in such soft inking ground, but on it rushed through all along its edge in every direction in the most wonderful manner. It then after returning from the seashore removed an old boiler from the docks to a yard some distance. The boiler and wagon with the fastenings chains weighed at least 22 tons and the boiler on the wagon stood at 25 feet high. For the cost of a few pounds of coal and water the job was done with ease.”
Numerous trials were run with this engine, drawing a large omnibus behind, at the rate of 10 to 12 miles an hour. It was found to be more practical to have a separate engine from the passenger carrying trailer. The general rule in Britain was to have one trailer, which was often a double decked affair, on two bogies or axles. One development was the engine and trailer shown in the accompanying illustration of a road steamer on trial between Granton and Leith in 1870.
From the illustration of the steamer it shows the horizontal engine and vertical pot boiler which were mounted upon a wrought-iron frame of channel iron, presenting a neat and compact appearance. This engine was subjected to trials with two 6-horse power engines, under Mr. Thompson's directions, which exhibited their tractive power and speed in a remarkable manner. The Scotsman Newspaper quoted these "One of the 6 ton road steamers was harnessed to four wagons of pig iron, weight of iron and wagons 34 tons, which it drew without an effort or any stoppage from the foot to the top of Granton Road, a distance of a quarter of a mile, with inclines of one in eighteen. Arrived at the top, it turned with its train and ran back to its starting point.” It should be pointed out that the drawing of 34 tons, besides the engine's own weight, up one in twenty, is equal to drawing about 100 tons or more on a level road.
The other road steamer was attached to an omnibus which conveyed a party of gentlemen from Granton to Leith. The distance is two and three-quarter miles, and the journey was performed at the rate of over eight miles an hour, that being the highest speed at which it was deemed safe to run through a town."
Soon the first omnibus was in service between Edinburgh and Leith. This light and compact road steamer had been built specially for omnibus traffic by Tennant & Company at their Bowershall works in Leith. Mr. A Ritchie was a local transport operator and he thought this machine might be an improvement on his horse buses that were in use between Edinburgh and Leith. The image shows the passenger carrying trailer built by Drew and Burnett. This passenger trailer vehicle was unusually carried on a single axle only, with space for 21 passengers inside and 44 passengers on top.
A passenger service was run between Portobello, which was a separate district from Edinburgh at this time, and Edinburgh which commenced on 2 June 1870.
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